Electromagnetic induction apparatus and method of forming same



Dec. 14, 1948. G. G. SOMERVILLE 2,456,453

ELECTROMAGNETIC INDUCTION APPARATUS AND METHOD OF FORMING SAME 2Sheets-Sheet 1 Filed May 22, I944 Inventor: Gareth G. Somerville b v uzfiadwua His AbbOT'he g.

1948- G. G.SOMERVILLE ,456,458

ELECTROMAGNETIC INDUCTION APPARATUS AND METHOD OF FORMING SAME Filed May22, 1944 2 Sheets-Sheet 2 Inveno ov: Gareth G. SOTTIGTYHIG,

H is AttOTneH.

Patented Dec. 14, 1948 ELECTROMAGNETIC INDUCTION APPARA- TUS AND METHODOF FORMING SAME Gareth G. Somerville, Pittsfield, Mass, assignor toGeneral Electric Company, a corporation of New York Application May 22,1944, Serial No. 536,749

'7 Claims.

My invention relates to electromagnetic induction apparatus and magneticcores of the curved iron type, to a method of producing the core, and toa method of producing the assembled magnetic core and winding for theapparatus.

Electromagnetic induction apparatus have been formed with cores of aplurality of assem- \bled flat punchings, or of a curved or bent stripof magnetic material, or of bonded powdered ron. The powdered iron typecore has usually been used in high frequency apparatus, the wound coretype has been used in the smaller distribution type transformers, andthe flat laminated type has been used in the larger distributiontransformers and power transformers.

In my application S. N. 536,748, filed concur-, rently herewith andassigned to the same assignee as this present invention, I havedescribed and claimed a curved iron type core for electromagneticinduction appartus which may be efficiently applied to a relatively widerange of transformer sizes. This curved iron type core includesgenerally the use of a plurality of sheets of magnetic material formedof magnetic strip having the most favorable magnetic direction in linewith the flux path and assembling the sheets, which sheets are assembledand given the shape the core will have in the finished apparatus. Thecore is then annealed in this position, and assembled around a preformedconductive winding structure with a minimum of flexure of the magneticsheets. My improved curved iron type core and method of forming the corewhich forms the subject matter of the present application may beemployed to produce any suitable type of joint construction, and incertain types of electromagnetic induction apparatus, such as reactors,it is desirable to have both an air gap and an overlapped or staggeredbutt joint, and it is therefore a general object of my invention toprovide an improved electromagnetic induction apparatus which will havean air gap in one leg and an overlap joint in another leg.

A further object of my invention is to provide an improved method offorming a curved iron type core for an electromagnetic inductionapparatus.

A still further object of my invention is to provide an improved methodof producing an assembled magnetic core and winding for anelectromagnetic induction apparatus.

Further objects and advantages of my invention will become apparent fromthe following (Cl. 29155.6l)

description referring to the accompanying drawing, and the features ofnovelty which characterize my invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

Referring to the drawings, Fig. 1 illustrates a perspective view of atransformer which is provided with an embodiment of my invention; Fig. 2is a perspective view of the two groups of magnetic sheets to form eachof the cores of Fig. 1, and a ring within which the sheets from each ofthe groups are assembled; Fig. 3 illustrates the laminations assembledin the ring of Fig. 2; Fig. 4 is a fragmentary view of the magneticsheets expanded with the adjacent ends of the laminations in generalabutting relation; Fig. 5 is an exploded perspective view of theassembled magnetic sheets and the form used to expand the core; Fig. 6illustrates the core during a further step in giving the core the shapeit will have in the finished apparatus; Fig. '7 is a side view of thecore in the shape it has when inserted into an annealing furnace; Fig. 8illustrates the reactor of Fig. 1 with one core assembled around one ofthe legs of the winding and the other core in the process of beingassembled, and Fig. 9 illustrates an electromagnetic apparatus with thesheets having a modified joint construction.

Referring to Fig. 1 of the drawings, I have illustrated anelectromagnetic induction apparatus including a preformed conductivewinding structure l with cores 2 and 3 passing through the window of thewinding and surrounding legs thereof. A core clamp is provided in theform of U-shaped bars 4 and 5 which are placed on either side of thecores and forced together by bolts 6.

In the construction illustrated in Fig. 1, two cores are provided withlegs passing through the winding window, but it is to be understood thatany suitable number of cores may be employed. As will be seen moreclearly in Fig. 8, each of the cores 2 and 3 includes two U-shaped coreportions 1 and 8 with air gaps 9' between the adjacent ends of the legportions 9 and I0 within the winding window and overlapping or staggeredbutt joints II between the outer leg portions H and I2. Such aconstruction may be employed with any suitable type of electromagneticinduction apparatus but this construction has particular application toa reactor. Since each of the cores 2 and 3 are similar, only one will bedescribed below in connection with Figs 2 through 7.

In order to produce the magnetic core 2, I provide two groups of sheetsof magnetic material, the groups being indicated generally by thenumerals l3 and M in Fig. 2. The magnetic sheets may be formed in anysuitable manner such as by cutting from magnetic strip material havingthe most favorable magnetic direction longitudinally of the strip.Furthermore, as

will be seen from Fig. 2, the magnetic sheets are Fig. 2 may beassembled in any suitable manner to produce my improved core and I haveillustrated in Fig. 2 a band I! into which the sheets may be assembledto produce the core. The machine including this band upon which thelaminations are assembled is described in further detail in myapplication S. N. 536,748, which has been referred to above.

In order to assemble the various sheets from the groups |3 and I4 intothe band, the longest sheet l6 from the group I4 is inserted inside theband by bending it sufficiently so as to generally follow the contour ofthe inside suriace oi the band. In order to facilitate assembly of thevarious sheets inside the band I5, pins l7 and II are anchored in plateI! and extend inward. It will also be seen that the various sheets whichmake up the group I4 each have an opening positioned slightly from oneend thereof. Thus, upon introduction of the sheet l8 within the band thepin I1 is passed through the opening 20. A corresponding sheet 2| of thegroup II is then removed and introduced into the band I! so that in thefinished core the sheet l6 from the group I4 and the corresponding sheet2| from the group I3 will make one complete layer. Referring to Fig. 4,it will be seen that an end 22 of the sheet IE will abut thecorresponding end 23 of the sheet 2|. However, for convenience inassembly the ends 22 and 23 oi! the sheets l6 and 2|, respectively, areallowed to stay in overlapping relation until an suitable number areassembled. The sheets, however, may be made to have the ends 22 and 23butt against each other by expanding and curving them sufllciently whenthey are inserted within the ring.

As will be seen, particularly in relation to Figs. 3 and 4, the totallength of the sheets I6 and 2| make up one complete layer with the ends22 and 23 in abutting relation, and the opposite ends 24 and 25 also inabutting relation or with a gap therebetween, as desired. It will benoted, however. that the ends 22 and 23 are not placed directly oppositethe gap between the ends 24 and 25, and assuming that the gap made bythe ends 24 and 25 will be in approximately the center of the leg 9-H),the joint between the ends 22 and 23 as shown in Figs. 3 and 4 will bedisplaced slightly to the right of the center line 28. The joint betweenthe ends 22 and 23 may be displaced any suitable amount by merelyvarying the relative lengths of the sheets I! and 2|, and in theconstruction illustrated in Fig. 3 the sheet I6 is longer than the sheet2| by the amount in which the joint between the ends 22 and 2| extendsto the right or the center line 24.

In order that the joints in the outside leg made or the portions H andi2 will be staggered so as to provide overlapping butt joints, while thejoints between the inner leg portions 4 and II will all beinyregistry soas to provide a straight gap. the next layer formed of sheets adjacentthe sheets |4 and 2| will be so formed that a sheet from the group I3will be placed contiguous with sheet i8 0! thegroup |4. Thus reierringto Fig. 2, a sheet 21 is taken from the group i2 which is the nextshorter sheet of the group II adjacent the sheet 2| and introduced intothe ring with the pin l1 passing through the opening 28, and the sheet21 extending around the ring to the leit looking at Fig. 3 and adjacentthe sheet ll. Similarly, a sheet 28 is taken from the group I4 andintroduced into the ring with a pin ll passing through the opening 20 ofthe sheet and the sheet extending around to the right adjacent the sheet2|. Since the sheet 28 islonger than sheet 21 by the same amount thatthe sheet I. is longer than the sheet 2|, the ends 30 and 4| of thesheets 21 and 28, respectively, will in the finished core provide a buttjoint to the left of the center line 28 as will be seen in Fig. 4, Thusproviding a closed magnetic core by assembling sheets from two groups inwhich the sheets of one group are slightly longer than one-half theperiphery and the corresponding sheets of the other group being slightlyless than one-half the periphery and with the sheets of each group beingassembled alternately, an overlap butt joint will be provided in one oi!the legs. Since the holes 20 and 28 are provided the same distance fromthe adjacent ends of the sheets it will be seen that in the opposite legthe various ends of the sheets will be placed in registry so as toprovide either a butt joint or a straight sided gap across the leg |l-|2of the finished core.

Alter all .the sheets have been introduced as is illustrated in Fig. 3and described above, the various overlapping ends may be placed inabutting relation by applying pressure to fingers 42 and 23 in themanner described in my application 8. N. 536,748. This will cause theends to be pulled slightly apart in the manner as shown in Fig. 4 afterwhich they may be forced together so as to provide a relatively tightbutt joint between the adjacent ends of the sheets from each of thegroups. Instead oi. stacking one sheet at a time from each group, anyother suitable number from each group may be stacked at one time.

The core may then be used in a circular form or it may be expanded byusing an expansion type wedge, as is illustrated in Fig. 5, includingtwo similar blocks 34 with a wedge member 35. The introduction of thewedge shaped mandrel in the position as illustrated in Fig. 5 and thenthe forcing of the wedge 25 into the position as is illustrated in Fig.6, will elongate the core. However, since the joints are placed inopposite legs the use of the expansion mandrel may cause the Joints toopen up, and in order to complete the expanding operation as well as tocause the adjacent ends of the sheets to fit relatively tightly togetherthe core may be introduced into a press, one leg of the core being puton a base of the press and the press having movable pistons 38, 31 and38. Thus by pressing on the core from four opposite sides the core maybe given the oblong configuration as is illustrated in Fig. 7. In orderto hold the core in this position a bracket is placed around the corehaving plates 39 and 4|! which are held tightly on either side of thecore by means of bars ll and 42, which may be attached to the plates inany suitable manner such as by spot welding. In order to remove alldeleterious strains and give the sheets a permanent set in the positionthey will have in the final core, the core construction as illustratedin F18. '7 may be placed in an oven and given a suitable strainreliefanneal.

In order to assemble the core around the leg of a preformed conductivewinding structure the brackets 39 and 40 are removed and the U-shapedcore portions disassembled by pulling them apart by applying force tothe U -shaped members 1 and 8 in the opposite directions, which forcewill be parallel with the longitudinal axis of the core. Rivets 43 maybe introduced through the holes so as to relatively tightly hold theadjacent ends of the sheets together. The two U-shaped portions 1 and 8are then assembled with the preformed coil winding structure I byprojecting the legs 9 and in into the winding window with their endsforming an air gap or a registering but joint. Upon holding the ends inthe desired relation inside the winding window the outer ends of thecore are pulled outwardly in any suitable manner such as by graspingwith hands, as is illustrated diagrammatically in Fig. 8. Thelaminations are then allowed to slip back into position by allowingfirst one lamination from the core portion 1 and then the correspondingsheets from the core portion 8 to drop into place. Thus a longer sheet44 from the core portion 1 is allowed to drop into place and then thecorresponding shorter sheet 45 from the core portion 8 until the endsare in abutting relation as is illustrated in Fig. 8. The various sheetsare then allowed to slip back into place until the core takes theposition as is illustrated by the core 3 in Fig. 8, which core is shownas already assembled around the conductive winding structure. It willalso be noted that a strip of insulating material 46 has been placedbetween the adjacent ends 9 and I0 of the leg portions so as to fix thelength of the air gap but it is to be understood that the ends may beplaced in abutting relation without the insulating sheet if desired. Inorder that the ends may not be strained with the use of the layer 46 thecore before anneal has a metal piece 41 of the same dimensions as thesheet 46 between the leg portions 9 and H).

In Fig. 9 I have illustrated a modification of m invention including apreformed winding 50 which is assembled with two cores includingU-shaped portions 5| and 52 which form one core and U-shaped portions 53and 54 which make up the other core. In the construction illustrated inFig. 9, rivets 55 and 55 tightly hold together the adjacent sheets ofboth of the cores which make up the legs which project into the windingwindow. Thus the cores are assembled with the preformed coil byintroducing the U-shaped members 5| and 53, and 52 and 54 from oppositedirections to form the gap or butt joint 51 and then forming the overlapbutt joint in the outer legs in the same manner described above inconnection with Fig. 8. It will also be seen that in the constructionillustrated in Fig. 9 there is a build-up on the two outer legs in thevicinity of the joints and this particular joint is more completelydescribed in my application S. N. 553,523, filed September 11, 1944, andassigned to the same assignee as this present invention.

Although I have shown and described particular embodiments of myinvention, 1 do not desire to be limited to the embodiments described,and I intend in the appended claims to cover all modifications which donot depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of producing an assembled magnetic core and winding for anelectromagnetic induction apparatus including the steps of cutting frommagnetic strip material at least two groups of sheets each having alength less than the total length of the perimeter of the finished coreand with the lengths of the sheets of each group having progressivelydifierent lengths, assenibling the sheets of both groups to provide aclosed core of a plurality of layers and providing the longer sheets ofeach group at the outer periphery with each layer including one sheetfrom each group and with the sheets of each group being assembledalternately, aligning the ends of the sheets to provide aligned jointsin one portion of the core and staggering the opposite ends to providestaggered butt joints in another portion of the core, applying pressureat both the inside and outside surfaces of the assembled core structureso as to abut relatively closely adjacent ends of the sheets of eachlayer and to provide a relatively tight laminated structure with theshape the core will have in the finished apparatus, annealing the core,and disassembling the groups of sheets into two core portions andreassembling the two core portions around the winding.

2. The method of producing an assembled magnetic core and winding for anelectromagnetic induction apparatus including the steps of cutting frommagnetic strip material two groups of sheets having progressivelydifferent lengths with the corresponding sheets of one group having alength slightly more than one-half the total perimeter and thecorresponding sheet of the other group having a length slightly lessthan one-half the perimeter of the core at a predetermined layer in theassembled core structure, and assembling the sheets of both groups toprovide a plurality of layers and providing the longer sheets of eachgroup at the outer perimeter with each layer including one sheet of eachgroup and with adjacent sheets being from different groups so as tostagger the butt joints at at least one side of the core, applyingpressure at both the inside and outside surfaces of the assembled corestructure so as to abut relatively closely adjacent ends of the sheetsof each layer and provide a relatively tightly laminated structure withthe shape the core will have in the finished apparatus, annealing thecore, and disassembling the groups of sheets into two core portions andreassembling the two core portions around the winding.

3. The method of providing a core for an electromagnetic inductionapparatus including the steps of providing two groups of sheets ofmagnetic material, the corresponding sheets of each group havingdifferent lengths and the total length of any two corresponding sheetsof the groups being equal to the total perimeter of the assembled coreat a predetermined layer, and assembling one sheet from each group withends in predetermined spaced relation to provide a layer, and assemblingan adjacent layer of one sheet from each group with ends inpredetermined spaced relation and with the sheets of one group lyingcontiguous with the sheets of the other group.

4. The method of forming a core for an electromagnetic inductionapparatus including the steps of providing two groups of sheets ofmagnetic material of progressively different lengths, with correspondingsheets of each group having diflerent lengths and with holes spaced thesame distance from one end of the sheets, and assembling a plurality ofsheets from each group so that one sheet from each group forms a layerin the finished core and aligning holes oi con tiguous sheets so thatthe ends provide a smooth faced gap in one portion of the core, theassembling step including placing sheets from both groups contiguouslyso that ends of adjacent sheets will overlap in another portion of thecore.

5. The method oi! producing an assembled magnetic core and winding foran electromag netic induction apparatus including the steps of providingtwo groups of sheets having progressively different lengths with thecorresponding sheets of one group having a length slightly more thanone-half the total perimeter and the corresponding sheet of the othergroup having a length slightly less than one-half the perimeter of thecore at a predetermined layer in the assembled core structure,assembling the sheets with one sheet from one group adjacent a sheetfrom the second group with the longer sheets at the outer perimeter soas to provide a core with aligned joints in one leg and staggered buttjoints in the other leg, annealing the core, disassembling the core intotwo U-shaped core portions, placing the legs of the U-shaped portionshaving the aligned joints in a winding window, and slightly flexing thesheets of the outer leg so as to place'the adjacent sheets of the coreportions with overlapping ends and in the position subsequent to anneal.

6. The method of providing a core for an electromagnetic inductionapparatus including the steps of providing two groups of sheets ofmagnetic material of progressively different lengths, and assembling onesheet from each group to form at least a portion of a layer of the core,and formlng at least a portion of an adjacent layer by assembling onesheet from each group and with the sheet of one group in one layer lyingcontiguous with the sheet from the other roup in the adjacent layer.

7. The method of linking a conductive winding with a magnetic core whichcomprises building up a laminated magnetic loop from a plurality of bentmagnetic strips in which each layer consists of two unequal lengthstrips, providing a substantially equal registering gap between one pairof ends of the strips in each layer, providing a butt joint between theother pair of ends of the strips in each layer, reversing the inequalityin length of said strips in certain of said layers so as to stagger saidbutt joints, mechanically forcing said loop into a generally rectangularshape with said gap in one straight leg and said staggered butt joint inthe opposite straight leg, annealing said core, separating said core atsaid gap and butt joints into two U-shaped members, placing the legs ofsaid members whose ends form said gap into the window of said conductivewinding from opposite sides thereof, and flexing the other legs of saidmembers so as to interleave said strips and reform said staggered buttjoints.

' GARETH G. SOMERVILLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 750,525 Everest Jan. 26, 19041,102,513 Johannesen July 7, 1914 1,365,569 Troy Jan. 11, 1921 1,457,619Cohen June 5, 1923 1,933,140 Gakle Oct. 31, 1933 2,055,175 Franz Sept.22, 1936 2,252,461 Franz Aug. 12, 1941 2,318,095 Putman May 4, 1943FOREIGN PATENTS Number Country Date 106,986 Great Britain June 14, 1917

